Data storage technology over the years has evolved from a direct attached storage model (DAS) to using remote computer storage models, such as Network Attached Storage (NAS) and a Storage Area Network (SAN). With the direct storage model, the storage is directly attached to the workstations and application servers, but this creates numerous difficulties with the administration, backup, compliance and maintenance of the directly stored data. These difficulties are alleviated at least in part by separating the application server/workstations from the storage medium. For example, FIG. 1 depicts a typical NAS system 100 in which a number of PCs, workstations and application servers (clients) use a network 10 to access storage resources on a number of remote network attached storage and file servers (or filers). In the depicted system 100, each of the networked PC or workstation devices 12-14 and application servers 16-18 may act as a storage client that is connected to the network 10 by the appropriate routers 11 and switches 15 to remotely store and retrieve data with one or more NAS filers 1-6, which in turn are connected to the network 10 by the appropriate routers 9 and switches 7-8. Typically, the storage clients (e.g., 14) use an IP-based network protocol, such as CIFS and NFS, to communicate store, retrieve and modify files on an NAS filer (e.g., 5).
Conventional NAS devices are designed with data storage hardware components (including a plurality of hard disk drives, one or more processors for controlling access to the disk drives, I/O controller and high speed cache memory) and operating system and other software that provides data storage and access functions. Even with a high speed internal cache memory, the access response time for NAS devices continues to be outpaced by the faster processor speeds in the client devices 12-14, 16-18, especially where anyone NAS device may be connected to a plurality of clients. In part, this performance problem is caused by the lower cache hit rates that result from a combination of larger and constantly changing active data sets and large number of clients mounting the NAS storage device.